Nondetonating blasting explosive



Patented Apr. 11, 1939 UNITE STATES NONDETONATING BLASTIN G EXPLOSIVEain No Drawing. Application August 4, 1937, Serial 5 Claims.

The present invention relates to non-detonating blasting explosives.Such explosives are suitable for use when a slow heaving action ratherthan a ripping action is required, and hence find extensive use in coalmining.

' In the class of detonating explosives, compositions of quite a varietyof types have hitherto found application; for instance, gelatinous andnon-gelatinous nitroglycerine explosives, chlorate and other Sprengelexplosives, ammonium nitrate and nitrobody explosives and liquid oxygenexplosives. On the other hand, however, in the class of non-detonatingexplosives, with which the present invention is concerned, practicalapplication has been confined hitherto almost entirely to blackpowder ormodifications of blackpowder. Within more recent years pressureventingblasting devices charged with liquid carbon dioxide and a heater havefound some application in coal mining; and a composition based on amixture of sodium nitrite and ammonium chloride has recently beenproposed for use in such devices. The present invention, however, isconcerned only with explosives adapted to blast after being loadeddirect into a borehole and tamped in the usual manner.

An objection to the use of unmodified blackpowder in coal mines is thatits explosion is accompanied by a flame that will ignite a dangerousmine atmosphere. On this account, blackpowder is excluded from animportant field, in which its characteristic properties would otherwiseensure its extensive use, in favour of certain detonating explosives andother blasting devices that are safe in gas.

The present invention is concerned with the production of non-detonatingexplosives having the heaving action characteristic of gunpowder, andhaving in some cases the additional advantage that their combustion isfiameless and does not ignite a dangerous mine atmosphere.

It is already ,known that the salts of hypophosphorous acid haveexplosive properties; and it has been proposed to employe thehypophosphites, particularly of sodium potassium and ammonium, inconjunction with a fulminate or fulminatechlorate detonator, asdetonating explosives for military or commercial purposes. It has alsobeen proposed to employ such hypophosphites in admixture with oxidizingagents such as nitrates, chlorates or dioxides, the amount of suchoxidizing agent varying from 10 to 50%.

'Ihe decomposition of the hypophosphites, or of the known compositionscontaining them, is accompanied by flame. For example, mixtures of InGreat Britain August 10,

ammonium hypophosphite and ammonium or potassium nitrate in allproportions that form self-combustible mixtures burn with flame; and theaddition of a cooling salt with a view to the reduction of the fiameeither hinders the propagation of combustion without producing thedesired effect, or renders the composition incapable of self-combustion.Mixtures of other hypophosphites with oxidizing salts give compositionsof comparatively poor combustibility which, if they burn at all, burnwith fiame. Further, many of such explosive mixtures have to be verycarefully protected from moist atmospheres.

This invention has as an object to produce new non-detonating blastingexplosives. A further object is to produce non-detonating blastingexplosives which will explode without flame. A further object is toproduce non-detonating blasting explosives which will not be easilydamaged by moist atmosphere. A further object of this invention is toprovide methods of manufacturing such explosives. Further objects willappear hereinafter.

These objects are achieved by the following invention. I have found thatif, in a mixture of ammonium nitrate, with or without cooling salt, andan alkali metal hypophosphite, the ammonium nitrate is replaced by asalt pair forming ammonium nitrate and a cooling salt by metathesis,compositions are formed which are self-combustible when locally ignited,closely resemble blackpowder in their rate of pressure-development underconfinement, and in some cases present the additional advantageousfeature that their combustion is fiameless, thereby rendering thecompositions suitable for use as non-detonating explosives in fiery anddusty mines. A further advantage of these compositions is that they donot require to be protected from moist atmospheres as do ammoniumnitrate compositions.

According to the present invention, a non-detonating blasting explosivecomposition comprises an alkali metal or preferably ammoniumhypophosphite, and a mixture of an ammonium salt and an alkali metalnitrate; the said mixture being adapted to form by metathesis a mixtureof ammonium nitrate and a cooling salt such as a sulphate, carbonate,bicarbonate, or chloride of the alkali or alkaline earth metals, andcontaining if desired an initial proportion of either or both of thelatter salts in the free state.

The proportion of hypophosphite used is sufficient to render thecomposition self-propagating when locally ignited; but is insufficientto cause it to burn with flame. For example, an equimolar a gun into a9% methane-in-air mixture.

total composition, i.

mixture of potassium nitrate and ammonium chloride containing as littleas 3.5% of ammonium hypophosphite will propagate its own combustion; butthe best results with mixtures of these salts are obtained when theproportion of ammonium hypophosphite is about 20% of the e.', aboutone-half molar proportion. As mixtures containing the higher proportionsof hypophosphite evolve gases containing hydrogen and phosphine, andthereby may cause an objectionable fume, I may add a small proportion ofan oxidising agent, preferably ammonium nitrate, for the purpose ofimproving the oxygen balance of the composition; also adding ifnecessary a small proportion of a cooling salt to offset any consequentincreased tendency to combustion with flame.

The compositions of my invention may be prepared by incorporation of thedry ingredients, for instance by milling, followed by granulation ifdesired. In order to ignite the compositions I may use igniting devicesadapted to produce a local supply of heat, for instance a safetyigniter. The non-detonating composition may also be initiated by meansof the heat developed by a blasting detonator; detonation of thecomposition does not occur.

The invention is further illustrated by the following example in whichhe parts are parts by weight.

' Example 101 parts potassium nitrate, 53.5 parts ammonium chloride,41.5 parts ammonium hypophosphite, and 20 parts ammonium nitrate, all inthe form of crystalline powders, are ground together.

in a mill. The mixture is then pressed and granulated. A No. 6 fulminatechlorate 80:20 detonator, or a safety igniter, may be employed forigniting the granular mixture in the borehole. No ignition occurs in thegallery test when 12 oz. of this composition are tested by being firedfrom Exposed 4 oz. charges of the composition may be fired either bysafetyigniters or by blasting detonators in the same atmosphere withoutcausing any ignition of gas.

Examples of the hypophosphites suitable for this invention are:ammonium, potassium and sodium hypophosphites, which can be used in themanufacture of safety explosives according to the invention. Otherhypophosphites, e. g. iron, calcium or barium hypophosphites, may beused where the production of flame during the explosion is notundesirable.

Examples of the salt pairs which form ammonium nitrate by. metathesisare: ammonium sulphate and sodium nitrate or potassium nitrate; ammoniumcarbonate or bicarbonate and sodium or potassium nitrate; ammoniumchloride and a nitrate of sodium, potassium, calcium, strontium orbarium.

This invention is a valuable advance in the art as it extends the rangeof known non-detonating explosives and certain of them possess a marginof safety from ignition from fiery or dusty atmospheres which is greaterthan that of the known safety detonating explosives of commerce.

As many apparently widely different embodiments of this invention may bemade Without departing from the spirit and scope thereof it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. A. non-detonating blasting explosive comprising a compound selectedfrom the group consisting of the ammonium and alkali metalhypophosphites, and a salt mixture containing ammonium salt selectedfrom the group consisting of ammonium sulphate, carbonate, bicarbonate,and chloride and a second salt taken from the group consisting of thealkali and alkaline earth nitrates, said salt mixture being adapted toform by metathesis a mixture of ammonium nitrate and a cooling saltselected from the group consisting of the sulphates, carbonates,bicarbenates, and chlorides oi the alkali or alkaline earth metals.

2. An explosive as claimed claim 1 containing an additional portion ofoxidising agent.

3. An explosive as claimed in claim i containing an additional portionof ammonium nitrate.

4. An explosive claimed in claim 1 containing an additional portion of acooling salt.

5. An explosive as claimed in claim 1 in which the proportion ofhypophosphite in the total composition does not exceed one nalf molarproportion.

ALEXANDER THOMSON TYRE.

